我试图像在Android中为RecyclerView适配器所做的那样,在AnimatedList上预生成所有更新操作。但是当我要清除所有数据时,我不知道该怎么做。
如果我这样做
setState(() {
_data.clear();
});
然后清除了备份数据,但是GlobalKey的当前状态仍然不知道更改,并且没有clear()
方法。
补充代码
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
appBar: AppBar(title: Text('Update AnimatedList data')),
body: BodyWidget(),
),
);
}
}
class BodyWidget extends StatefulWidget {
@override
BodyWidgetState createState() {
return new BodyWidgetState();
}
}
class BodyWidgetState extends State<BodyWidget> {
// the GlobalKey is needed to animate the list
final GlobalKey<AnimatedListState> _listKey = GlobalKey();
// backing data
List<String> _data = ['Horse', 'Cow', 'Camel', 'Sheep', 'Goat'];
@override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
SizedBox(
height: 400,
child: AnimatedList(
key: _listKey,
initialItemCount: _data.length,
itemBuilder: (context, index, animation) {
return _buildItem(_data[index], animation);
},
),
),
RaisedButton(
child: Text(
'Clear all items',
style: TextStyle(fontSize: 20),
),
onPressed: () {
_clearAllItems();
},
)
],
);
}
Widget _buildItem(String item, Animation animation) {
return SizeTransition(
sizeFactor: animation,
child: Card(
child: ListTile(
title: Text(
item,
style: TextStyle(fontSize: 20),
),
),
),
);
}
void _clearAllItems() {
_data.clear();
// no such method
_listKey.currentState.clear();
}
}
答案 0 :(得分:4)
您必须手动删除_listKey.currentState
中的项目
示例代码:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
appBar: AppBar(title: Text('Update AnimatedList data')),
body: BodyWidget(),
),
);
}
}
class BodyWidget extends StatefulWidget {
@override
BodyWidgetState createState() {
return new BodyWidgetState();
}
}
class BodyWidgetState extends State<BodyWidget> {
// the GlobalKey is needed to animate the list
final GlobalKey<AnimatedListState> _listKey = GlobalKey();
// backing data
List<String> _data = ['Horse', 'Cow', 'Camel', 'Sheep', 'Goat'];
@override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
SizedBox(
height: 400,
child: AnimatedList(
key: _listKey,
initialItemCount: _data.length,
itemBuilder: (context, index, animation) {
return _buildItem(_data[index], animation);
},
),
),
RaisedButton(
child: Text(
'Clear all items',
style: TextStyle(fontSize: 20),
),
onPressed: () {
_clearAllItems();
},
)
],
);
}
Widget _buildItem(String item, Animation animation) {
return SizeTransition(
sizeFactor: animation,
child: Card(
child: ListTile(
title: Text(
item,
style: TextStyle(fontSize: 20),
),
),
),
);
}
void _clearAllItems() {
for (var i = 0; i <= _data.length - 1; i++) {
_listKey.currentState.removeItem(0,
(BuildContext context, Animation<double> animation) {
return Container();
});
}
_data.clear();
}
}
答案 1 :(得分:1)
每次将新密钥传递给AnimatedList
小部件时,它将重新创建其状态并在下次使用全新的项目列表进行重建:
var _listKey = GlobalKey<AnimatedListState>();
void _clearAllItems() {
_data.clear();
setState(() => _listKey = GlobalKey());
}